The core part of a helicopter is its main rotor. One or more driving mechanisms actuate the main rotor via one transmission and one rotor mast which is rotatably supported in the housing of the transmission and on which the rotor head is fastened.
With its two and more rotor blades, which are adjustably connected with the rotor head around the longitudinal axis thereof, the main rotor takes care not only of the lift but also of the propulsion. The rotor blades are hinged on the rotor head via a flapping hinge and a drag link or via a torsionable rod. To produce a lift, the rotor blades are adjusted collectively, that is, synchronously around an angle formed with the rotation plane. A propulsion is obtained by a cyclic control, that is, during a revolution of the rotor mast the angle of incidence of a rotor blade runs through a maximum and a minimum. The direction of flight determines the position of the extreme values.
The helicopter pilot controls the rotor blades via a swash plate. The latter consists of a stationary part which, via a so-called fork, is fastened on the housing of a transmission in a non-rotational but axially displaceable manner, and tiltably in all directions relative to the rotor mast, and of a rotatable part which is rotatably supported by radial and axial bearings against the stationary part. The rotatable part moves with the stationary part-in the axial direction, also performing at the same time tilting movements. It is fastened on the rotor head via another fork.
The movement of the swash plate is transmitted via a lever mechanism to rotor blade holding fixtures on the rotor head, and this mostly in a manner such that the angle of incidence of a rotor blade enlarges approximately with the angle of the swash plate to the rotor head.
For the flying maneuvers the helicopter pilot adjusts the swash plate via one other lever mechanism. Parallel to the latter are often mounted hydraulic servomotors which, on one hand, facilitate the control and, on the other, make a superposed control possible which counteracts the rotor blade oscillations that occur.
U.S. Pat. No. 3,080,002 has disclosed a helicopter drive mechanism on which a rotor mast is rotatably supported in a transmission housing, specifically on the outer periphery thereof, directly on the transmission housing and on an inner cavity on a supporting column firmly- connected with the transmission housing. On the outer periphery of the rotor mast, a driving gear wheel is connected with positive fit with the rotor mast which is actuated, via a pinion, by a driving mechanism of the helicopter. A swash plate is situated above the rotor mast and the rotor head and is operated by actuators which are passed through the supporting column and the rotor mast.
The invention is based on the problem of better supporting the rotor mast in the transmission housing in a helicopter of the above mentioned kind and more conveniently introducing the forces from the transmission in the rotor mast. According to the invention this problem is solved by the features of claim 1.
According to the invention the rotor mast grows wider in funnel shape toward the housing of the transmission, the summarizing gear being flanged via a hollow stub shaft on the widened end of the rotor mast and the stub shaft and the rotor mast being together rotatably supported on a large diameter in the housing.
The funnel-shaped widening of the rotor mast reduces the stresses with increasing diameter so that the connection between the stub shaft or the summarizing gear and the rotor mast, which lies on a large diameter, is loaded with only very slight stresses. In addition, the driving and supporting forces are introduced in the transmission housing on the shortest path. Deformations in the meshing of gears are thereby extensively prevented. Besides, the number of parts becomes reduced due to the common support for the rotor mast and the summarizing gear.
Installation space is gained by virtue of the funnel-shaped widening of the rotor mast and the large supporting diameter, for ex., within the common bearing, in order to integrate the swash plate in the transmission housing. The swash plate can thus be supplied by the transmission lubrication and is protected against pollution from the outside.
In helicopters, where the rotor blades are fastened by flapping hinges and drag links on the rotor mast, the control rods engaging in the rotatable part of the swash plate can be guided by the rotor mast and the rotor head and engage in the rocking levers for the rotor blades which are rotatably supported in the rotor head. The control parts are thus altogether protected and the air flow is not impaired by outer control rods.
In helicopters where the rotor blades are fastened without flapping and drag hinges only via a torsionable rod on the rotor mast, it is required that the control rods extend outside the rotor mast. In order to protect the swash plate against weather influences and supply it by means of the transmission lubrication, according to an embodiment of the invention, the rod for control of the rotor blades is outwardly guided through the casing of the funnel-shaped part of the rotor mast by the rotatable part of the swash plate integrated in the transmission, the rod conveniently containing a shift lever supported on the rotor mast and flexibly connecting inner control rods with outer control rods.
In the specification and in the claims numerous features are shown and described in association. The expert will separately observe the combined features conveniently according to the problems to be solved and will form with them added logical combinations.